1. Field of the Invention
This invention relates to an X-Y position input device for computer systems, commonly known as a "mouse", which operates by sliding a casing on a base such as a desk top. It has a globe projecting on the under side of the casing which rolls on the base and the extent of rolling of the globe is output in terms of X- and Y-coordinates to provide coordinate values for the location of the mouse.
2. Description of the Prior Art
An input device of this type is, because of its good operability, used to move a cursor displayed on a CRT, for example, of an office computer, to input a starting point, turn point, and end point in drawing a picture, or to designate selective items displayed on the CRT, and permits, by using jointly together with a keyboard type input device, rapid and easy inputting of various data items.
The X-Y position input device is designed so that as its casing is moved on and along the surface of a horizontal stand, dedicated sheet, etc., the globe which partially projects through an opening formed in the bottom of the casing rolls on the surface (base). Usually, several means were incorporated in the bottom of the casing to ease the sliding action of the device on the base.
Describing illustratively, according to the prior art, the casing was formed of a hardened synthetic resin of good slidability and its under face was provided with a plurality of (usually, three) small projections, or a plurality of small-diameter bearings provided on the under side of the casing a portion each of which is made to project beyond the under face of the casing. However, the former had the problems in that the small projections wore with use thus deteriorating the sliding action; and the latter, though it was superior in wear resistance because of the use of the ball bearings, it had drawbacks in that the manufacturing costs were high and mechanical noise was generated when vibration from the rotating ball bearings was transmitted to the casing body.
A further different configuration of the X-Y position input device is also proposed in which an elastic member, such as nonwoven fabric or felt, is bonded to a certain position on the bottom face of the casing. Because this elastic member serves as a sliding surface against the base, this proposed configuration can prevent generation of mechanical noise. However, as the casing slides on the base which is comparatively hard and poor in slidability because it is made of hardwood, veneer etc. the elastic member tends to be worn away by the base.